Blood pump with flow cannula

ABSTRACT

A blood pump for supporting a patient&#39;s heart includes a flow cannula having a distal portion including a distal end and a proximal portion including a proximal end opposite the distal end, the distal end of the flow cannula configured to be connected to the patient&#39;s heart or a blood vessel to establish fluid communication between the blood pump and the patient&#39;s heart and blood vessel, respectively. The flow cannula further includes an intermediate portion attached to the distal portion and the proximal portion, wherein the intermediate portion allows twisting thereof with a lower force than the distal portion and the proximal portion. The intermediate portion can be fully occluded by twisting it. At least a portion of the intermediate portion either alone or in combination with the distal portion is adapted to be permanently attached to the patient&#39;s heart or a blood vessel.

BACKGROUND

This invention relates to a flow cannula for a blood pump for supportinga patient's heart. The flow cannula is configured for connecting theblood pump to the patient's heart or a blood vessel. The flow cannulacan be separated such that a part connected to the heart or blood vesselremains inside the patient's thorax after removing the blood pump. Theinvention further relates to a method of removing a blood pump from apatient.

Blood pumps may be inserted into a patient's vessel such as the aorta bymeans of a catheter, or may be placed in the thoracic cavity or evenoutside the patient's body. In some applications, and in particular inthose cases in which the blood pump is not placed intravascularly, itmay be necessary to establish a direct connection to a blood vessel orthe heart, e.g. the left ventricle. The flow cannula of the blood pumpis inserted into an opening of the heart and secured to the wall of theheart to establish a fluid communication between the blood pump and thepatient's heart. An outflow of the blood pump may then be connected tothe aorta to pump blood from the left ventricle directly into the aorta.

If the blood pump is no longer needed, e.g. because the heart hasrecovered, the blood pump is removed. However, complete removal of theflow cannula from the heart would usually require an open thorax surgeryand would involve a high risk of severe bleeding, and the opening in theheart would have to be closed. Therefore, the flow cannula is usuallyseparated, e.g. cut, such that the part connected to the heart remainsinside the patient's thorax. A clip, clamp or the like is used to closethe remaining part of the flow cannula. However, the flow cannula isusually cut close below the patient's skin to facilitate handling ifcomplications occur. Thus, the remaining part of the flow cannula isusually relatively long and the clamp may be bulky. This may affect thesurrounding tissue and may cause irritations or even inflammations.Apart from that, there may be a risk that the flow cannula, which may berelatively stiff and may have a relatively large diameter, cannot beclamped tightly such that blood leaks into the patient's thorax.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a flowcannula for a blood pump, and a blood pump with such a flow cannula,wherein the flow cannula can be easily occluded to stop the blood flowand subsequently separated, both preferably by a minimally invasiveprocedure, wherein further preferably interference of a part of the flowcannula that remains inside the patient with surrounding tissue can bereduced.

This object is achieved according to the present invention by a flowcannula and a method having the features of the independent claims.Preferred embodiments and further developments of the invention arespecified in the claims dependent thereon.

According to the invention, a flow cannula for a blood pump forsupporting a patient's heart comprises a distal end and a proximal endopposite the distal end along a longitudinal axis of the flow cannula.The distal end of the flow cannula is configured to be connected to thepatient's heart or a blood vessel in order to establish a fluidcommunication between the blood pump and the patient's heart and bloodvessel, respectively. The flow cannula comprises a distal portion havingsaid distal end, a proximal portion having said proximal end. The flowcannula further comprises an intermediate portion attached to at leastone of the distal portion and the proximal portion. The intermediateportion allows at least one of clamping and twisting, in particulartwisting, thereof with a lower force than at least one of the distalportion and the proximal portion. The intermediate portion is configuredto be fully occluded by twisting thereof. Throughout this disclosure,the term “distal” refers to directions away from a user, e.g. a surgeon,and towards the heart, whereas the term “proximal” refers to directionstowards a user.

At least a portion of the intermediate portion either alone or incombination with the distal portion is adapted to be permanentlyattached to the patient's heart or a blood vessel. In other words, saidportion of the intermediate portion either alone or in combination withthe distal portion is adapted to remain inside the patient's body afterremoval of the blood pump. Vice versa, preferably at least the proximalportion, possibly the proximal portion and the distal portion, incombination with the remaining part of the intermediate portion isadapted to be removed from the patient's body. Since only a small partof the flow cannula is left behind in the patient, fewer irritations andinflammations occur.

The flow cannula, which is designed in multiple portions, in particulara proximal portion, a distal portion and an intermediate portion allowsfor improved separation of the flow cannula during removal of the bloodpump, wherein the portion that will remain in the patient's body causesless interference with surrounding tissue. The flow cannula can beeasily occluded in a minimally invasive surgery by twisting theintermediate portion. In particular, the intermediate portion isconfigured to be twisted such it is fully occluded and a blood flowthrough the flow cannula is stopped. Twisting of the intermediateportion can be caused by twisting the proximal portion relative to thedistal portions because twisting of the intermediate portion requiresless force than twisting of at least the distal portion, preferably bothof the distal and proximal portions.

Since the intermediate portion requires less force for twisting orclamping or both clamping and twisting, it can be easily and securelyoccluded. A smaller clamp or clip compared to a clamp or clip that wouldbe necessary to occlude the distal portion is sufficient to occlude theintermediate portion of the flow cannula. Twisting of the intermediateportion allows for provisional occlusion of the flow cannula which maythen be finally closed by a clamp or clip or other suitable means, suchas a cable, wire or the like. Since lower forces are required tomanipulate the intermediate portion, the procedure of occluding the flowcannula and removing the proximal portion can be done minimallyinvasive, which bears less risk for the patient. Moreover, alternativelyor in addition to twisting the intermediate portion, a loop or cuttingwire can be used that is looped around the intermediate portion to clampit by pulling tight the loop or cutting wire. The term “clip” or “clamp”refers to a piece that is placed around the flow cannula, in particularthe twisted portion of the intermediate portion, to securely and finallyclose it such that the flow cannula can be cut or otherwise separated.The clip or clamp can be applied in a minimally invasive procedure. Incontrast to that, known cannulas may require bulky instruments, like ascissor-like surgical clamp, to stop the blood flow. This can be doneonly in an open thorax surgery.

The distal and proximal portions of the flow cannula may be releasablyconnected to each other, e.g. by a releasable connector, such as amale/female connector, threads, bayonet mount, quick coupling, magnetsor the like. Alternatively, the distal and proximal portions of the flowcannula may be connected via a predetermined breaking line, e.g. acircumferential notch. Thus, the proximal and distal portions can beseparated by a low force while the intermediate portion remains attachedto both the proximal portion and the distal portion.

Although releasably connected, however, inadvertent separation of theproximal and distal portions should be avoided. Therefore, in case apredetermined breaking line is provided, the predetermined breaking lineshould have a minimum resistance to withstand low breaking forces. Inparticular, it may be advantageous to design the predetermined breakingline such that an instrument, such as a hemostat or other clamp orcutting tool, is necessary to separate the proximal and distal portions.It may also be possible to protect the predetermined breaking line, e.g.by a cover, or a tear strip or the like may be provided. One or more,such as two, three, four, five or six, security filaments may beprovided attached to the proximal and distal portion, respectively, inorder to keep the proximal and distal portions together. The securityfilaments may be arranged outside the intermediate portion, e.g. evenlyspaced about the circumference of the flow cannula. They may be cut orotherwise separated in order to allow separating the proximal and distalportions from each other.

When separated from each other, the proximal and distal portions may beaxially movable with respect to each other, which may be achieved byaxially compressing or stretching the intermediate portion or bytwisting the intermediate portion, which causes the proximal and distalportions to get closer to each other. Alternatively, the distal andproximal portions may be integrally formed and intended not to beseparated. For example, the distal and proximal portions may form asingle tubular member, wherein the intermediate portion is placed overthe tubular member like a jacket.

More specifically, the intermediate portion of the flow cannula may havea distal end and a proximal end, the distal end of the intermediateportion being attached to the distal portion of the flow cannula and theproximal end of the intermediate portion being attached to the proximalportion of the flow cannula. Consequently, while the flow cannula isbeing prepared for complete separation no blood leaks from the flowcannula because the intermediate portion bridges the gap between theproximal and distal portions even when the proximal and distal portionshave been separated. It will thus be appreciated that the intermediateportion is preferably attached to at least the distal portion,preferably both the proximal and distal portions, in a fluid tightmanner in order to conduct a blood flow between the distal portion andthe proximal portion. For example, it may be glued, welded, clamped,bonded or otherwise attached. In embodiments, in which not both ends ofthe intermediate portion are attached, i.e. fixedly secured, to theproximal portion and distal portion, respectively, the respective freeend may be at least disposed on or about the respective end portion.

In an embodiment the intermediate portion is attached to the distal andproximal portions of the flow cannula such that it at least partiallyoverlaps at least one of, preferably each of, the distal and proximalportions of the flow cannula. That means that during operation of theblood pump, when the proximal and distal portions of the flow cannulaare connected to each other, the intermediate portion does not havecontact with the blood flowing through the flow cannula if it completelyoverlaps the proximal and distal portions. Thus, the intermediateportion can be made of a variety of materials that would not be suitablefor long term blood exposure. Further, the intermediate portion can bemade of a very thin material, which could bear the risk of tearing if ithad to conduct the blood flow during the entire operation of the bloodpump. Only during separation of the flow cannula, the intermediateportion will have direct contact with the blood flow as described inmore detail below. Thus, in particular but not exclusively in thisembodiment, the intermediate portion may have a wall thickness of lessthan about 150 μm, preferably about 30 μm, and may comprise a tubularpolymer film, such as polyethylene terephthalate (e.g. Dacron®),polyurethane or ePTFE. For instance, the wall thickness may range fromabout 5 μm to about 100 μm for polyurethane and from about 300 μm toabout 1,000 μm for ePTFE. The thin polymer film is particularly suitablefor twisting and thereby fully occluding the flow cannula as describedabove.

The intermediate portion may be gathered, in particular axiallygathered, when the distal and the proximal portions of the flow cannulaare connected to each other. The intermediate portion may behave in abellows-like manner, i.e. it may fold in a zig-zag manner, or it maysimply be compressed in an axial direction. If the intermediate portionis gathered or compressed when the proximal and distal portions areconnected, the intermediate portion can unfold or decompress when theproximal and distal portions are moved away from each other withoutstretching it. In other words, there is no tension on the intermediateportion when the proximal and distal portions are spaced apart. Thisallows for easy clamping and if necessary twisting of the intermediateportion without having to hold a tension on the intermediate portion,which is advantageous for a minimally invasive procedure. However, inany embodiment, the intermediate portion may be stretchable in adirection of the longitudinal axis.

Apart from that, in any embodiment the intermediate portion is sized anddimensioned not to interfere with an axial movement of the proximal anddistal portions, i.e. the intermediate portion is not too tight aboutthe proximal and distal portions. For instance, a slight gap may beprovided between the intermediate portion and at least one of,preferably both of, the proximal and distal portions. Since theintermediate portion may be attached to the proximal and distalportions, the intermediate portion may be slightly tapered, i.e. have aslightly larger diameter in the middle compared to its ends.

In another embodiment, in particular where the distal and proximalportions are integrally formed, the intermediate portion may comprise anattachment member, such as a disc at its distal end, which is configuredto be attached to the patient's heart, e.g. by suturing, in particularpermanently. Preferably, the proximal end of the intermediate portion isattached to the proximal portion. In this embodiment, the proximal anddistal portions of the flow cannula will not be separated but pulled outof the heart as a single piece. By pulling the proximal and distalportions, the intermediate portion will be stretched or unfolded asdescribed above such that it can be twisted and clamped. Theintermediate portion will be cut, such that only the attachment memberalong with a part of the intermediate portion is left behind in thepatient to close the opening in the patient's heart. The proximal anddistal portions are completely removed. In order to avoid inadvertentretraction of the proximal and distal portions, security filamentssimilar to those mentioned above can be provided, which are secured tothe attachment member and the proximal portion.

The attachment member is preferably made of a material that allowssuturing of the attachment member to the tissue of the heart, such as afelt or the like. In one embodiment the attachment member may compriseradially extending sections, such as three, four, five or six, with gapsbetween the sections. Upon twisting the intermediate portion, thesections will get closer to each other in a circumferential direction,such that the underlying heart tissue will be twisted and compressed ina circumferential direction about the opening to thereby narrow theopening in the heart tissue, in particular when the proximal and distalportions have been retracted from the heart. This reduces the wound sizeafter the flow cannula has been removed. The wound is then closed bymeans of the compressed attachment member and the part of theintermediate portion that remains inside the patient.

In still another embodiment the intermediate portion may be attached tothe distal and proximal portions such that the distal and proximalportions are axially spaced from each other and the intermediate portionis disposed between the distal and proximal portions. In other words,the proximal and distal portions are not directly connected to eachother but are connected via the intermediate portion. In thisembodiment, the intermediate portion conducts the blood flow duringoperation of the blood pump between the proximal and distal portions.Thus, in particular in this embodiment, the intermediate portion maycomprise a polymer tube, preferably silicone tube or polyurethane tube,which is suitable for long term blood exposure.

In any of the above described embodiments, the intermediate portion ispreferably a flexible tubular member. The proximal and distal portionsof the flow cannula preferably are tubular members, too. Advantageously,the distal portion of the flow cannula is as short as possible, ineither case shorter than the proximal portion of the flow cannula in alongitudinal direction, wherein a length of the distal portion ispreferably less than 50%, more preferably less than 25%, most preferablyless than 15% of a length of the proximal portion. For example, thedistal portion may have a length of 0.5 cm to 3 cm, e.g. 1 cm, and theproximal portion may have a length of 5 cm to 9 cm, e.g. 7 cm. The flowcannula may have a diameter of about 2 to 15 mm, preferably about 6 to 8mm.

Preferably, the blood pump is sized and configured to be placed in thepatient's thoracic cavity. This allows an application in which the bloodpump is fully implanted in a patient's body, e.g. connected to thepatient's heart and aorta. In other embodiments the blood pump mayinclude a pumping device that is configured to be placed extracorporeal,wherein the flow cannula extends through the patient's skin.

A system may comprise a blood pump as described above and at least oneclip or clamp that is sized and configured to be placed around theintermediate portion in order to fully occlude the flow cannula. Inparticular, the clip or clamp may be sized and shaped to be placedaround the intermediate portion when the proximal and distal portionsare spaced from each other. After the clip or clamp has been placedaround the intermediate portion, the proximal portion of the flowcannula can be removed, e.g. by cutting the intermediate portion asdescribed in more detail below.

An exemplary method of using the blood pump as described above, inparticular removing the blood pump from a patient, includes thefollowing steps. If the proximal and distal portions of the flow cannulaare connected, e.g. by means of a releasable connector or predeterminedbreaking line, the proximal and distal portions are separated andaxially moved apart from each other. The intermediate portion may thenunfold or stretch but remains connected to the proximal and distalportions. The intermediate portion is then occluded in order to occludethe flow cannula and stop the blood flow through the flow cannula. Ifnecessary or indicated by the application, the intermediate portion mayfirst be twisted in order to obtain a provisional occlusion. At the sametime, by twisting the intermediate portion its diameter is reduced,which makes it possible to use a small clip. The twisted or untwistedintermediate portion is then clamped by a clamp, clip or the like inorder to fully and definitely occlude the flow cannula. The proximalportion of the flow cannula can then be removed, e.g. by cutting theintermediate portion at a location proximal with respect to the clip.The distal portion along with part of the intermediate portion and theclip remains inside the patient. This procedure can be performedminimally invasively. The parts remaining inside the patient are smalland not bulky in order to reduce or avoid interference with surroundingtissue. Irritations and inflammations can be reduced or avoided.

In another exemplary embodiment, the proximal and distal portions form asingle piece and will not be separated. The intermediate portion has anattachment member at its distal end that is securely attached to thepatient's heart, while the proximal end of the intermediate portion isattached to the proximal portion of the flow cannula. Once the flowcannula is to be removed, the single piece comprising the proximal anddistal portions is pulled out of the heart, such that the intermediateportions unfolds and/or stretches. It is pulled far enough out of theheart to be able to twist and clamp and subsequently cut theintermediate portion. Only a distal part of the intermediate portionalong with the attachment member remains inside the patient. This canfurther reduce the size of material that is left behind in the patientand improve healing of the punch hole in the heart muscle.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofpreferred embodiments, will be better understood when read inconjunction with the appended drawings. For the purpose of illustratingthe present disclosure, reference is made to the drawings. The scope ofthe disclosure is not limited, however, to the specific embodimentsdisclosed in the drawings. In the drawings:

FIG. 1 shows a patient's heart with a blood pump attached thereto.

FIGS. 2a and 2b show an embodiment of a flow cannula.

FIGS. 3a to 3e show the flow cannula of FIGS. 2a, 2b during use.

FIGS. 4a to 4d show a flow cannula according to another embodimentduring use.

FIGS. 5a to 5e show a flow cannula according to another embodimentduring use.

FIG. 6 shows an intermediate portion according to one embodiment.

FIG. 7 shows an intermediate portion according to another embodiment.

FIGS. 8a and 8b schematically show an attachment member during use.

DETAILED DESCRIPTION

Referring to FIG. 1 a blood pump 1 is illustrated inserted into apatient's heart H. The blood pump 1 is placed in the thoracic cavity andis directly connected to the left ventricle LV of the heart H by meansof a flow cannula 4, which in this application is an inflow cannulabecause blood is drawn into the flow cannula 4, conveyed into a pumpcasing 20 through an inlet 2 by means of an impeller (not shown) in thepump casing 20, and further conveyed out of the blood pump 1 through anoutflow cannula 3 that is attached to the aorta AO. The flow cannula 4has a distal portion 5 secured to the wall of the heart H, a proximalportion 6 connected to the inlet 2 of the pump casing 20 and anintermediate portion 7 attached to the distal portion 5 and proximalportion 6 as described in more detail below. The blood pump 1 supportsthe patient's heart H. Once the blood pump 1 is to be removed, the flowcannula 4 is separated and the remaining distal part of the flow cannula4 is closed and left behind in the thoracic cavity.

The flow cannula 4 is illustrated in more detail in FIGS. 2a and 2b .FIG. 2a shows an unassembled view in order to illustrate the connection12 between the proximal and distal portions 5, 6. The proximal anddistal portions 5, 6 are releasably connected to each other, e.g. bymeans of a predetermined breaking line, which may be formed e.g. by acircumferential notch (see enlarged cutout), or by any other releasableconnector, such as threads, male/female connector, bayonet mount or thelike. The flow cannula 4 has a distal end 10 that is inserted into thepatient's heart H as illustrated in FIG. 1 and an opposing proximal end11 that is attached to the pump casing 20. The distal end 10 may besloped or tapered to facilitate insertion into the heart H.

The intermediate portion 7 has a distal end 8 that is attached to thedistal portion 5 and a proximal end 9 that is attached to the proximalportion 6 as shown in FIG. 2b . Thus, the intermediate portion 7overlaps both the distal portion 5 and the proximal portion 6. It willbe appreciated that the intermediate portion 7 may be attached to thedistal and proximal portions 5, 6 such that it overlaps only one ofthem. The intermediate portion 7 is gathered on the distal and proximalportion 5, 6. Since the distal and proximal portions 5, 6 are connectedas shown in FIG. 2a , the intermediate portion 7 does not have contactto the blood flowing through the flow cannula 4 during operation of theblood pump 1.

With reference to FIGS. 3a to 3e an exemplary method of removing a flowcannula from a patient's body, e.g. during removal of the blood pump 1of FIG. 1, including the flow cannula 4 of FIG. 2b , is described. Whilethe blood pump 1 is shown as a centrifugal blood pump, it will beappreciated that the flow cannula 4 can be used in combination withanother medical device, in particular another type of blood pump, suchas an axial blood pump or a mixed-type (centrifugal/axial) blood pump.FIG. 3a is substantially the same view as FIG. 2b and shows the flowcannula 4 during operation of the blood pump 1. After operation of theblood pump 1 has been stopped, the flow cannula 4 has to be separated toremove the proximal portion 6 from the patient. As illustrated in FIG.3b , the proximal portion 6 is separated from the distal portion 5 bydisconnecting the releasable connector 12, which may be done e.g. bybreaking the flow cannula 4 at a predetermined breaking line. Otherconnection mechanisms, such as a threaded connection may be used but arenot shown in FIG. 3b for the sake of simplicity. While the distalportion 5 remains attached to the patient's heart H, the proximalportion 6 is axially moved away from the distal portion 5. Theintermediate portion 7 unfolds or stretches and bridges the created gapbetween the distal and proximal portions 5, 6. Therefore, theintermediate portion 7 is attached to the proximal and distal portions5, 6 in a fluid tight manner.

Since the intermediate portion 7 is made of a thin polymer film, it canbe easily twisted to provisionally fully occlude the flow cannula 4 asshown in FIG. 3c to stop the blood flow through the flow cannula 4. Aclip 13 is then placed around the twisted intermediate portion 7 (FIG.3d ) for final occlusion and the intermediate portion 7 is separated,e.g. by cutting (FIG. 3e ). The remaining parts do not require muchspace in the thoracic cavity and can remain in the thoracic cavitywithout causing severe irritations or inflammations.

With reference to FIGS. 4a to 4d an exemplary method during removal of ablood pump according to another embodiment is described. In contrast tothe embodiment of FIGS. 3a to 3e , the flow cannula 14 comprises anintermediate portion 17 that does not overlap the distal and proximalportions 15, 16 but is disposed between them and connected to theproximal portion 15 with its proximal end 18 and to the distal portion16 with its distal end 19. Thus, the intermediate portion 17 is incontact with the blood flowing through the flow cannula 14 and ispreferably made of a material suitable for long term blood exposure,such as silicone or polyurethane. The intermediate portion 17 is not asthin as the intermediate portion 7 of the previous embodiment, but issofter than the distal and proximal portions 15, 16 to allow clampingand if applicable twisting thereof with a lower force than at least thedistal portion 15.

As shown in FIG. 4b , the intermediate portion 17 is twisted to create aprovisional full occlusion of the flow cannula 14 to stop the blood flowthrough the flow cannula 14. It will be appreciated that this step maybe omitted and that the clip 13 (FIG. 4c ) can be placed over thetwisted or untwisted intermediated portion 17 to create a full occlusionof the flow cannula 14. As in the previous embodiment, the intermediateportion 17 is then separated to remove the proximal portion 16 from thepatient, while the distal portion 15 remains attached to the patient'sheart H (FIG. 4d ).

With reference to FIGS. 5a to 5e an exemplary method during removal of ablood pump according to yet another embodiment is described. The flowcannula 24 includes a jacket-like intermediate portion 27 that comprisesan attachment member 30, which may be in the form of a disc, plate orsheet, at its distal end 29 opposite the proximal end 28, which is shownin more detail in FIGS. 6 and 7. The attachment member 30 is directlyattached to the patient's heart H, e.g. sutured, and is configured tostay attached to the heart H permanently. Except for the attachmentmember 30, the intermediate portion 27 is substantially similar to theintermediate portion 7 of the embodiment of FIGS. 3a to 3e , e.g. withrespect to the material and rigidity characteristics. The flow cannula24 comprises a tube having a proximal portion 26 and a distal portion 25that are integrally forming. In contrast to the previous embodiments,the proximal portion 26 and distal portion 25 will not be separated butare formed as a single piece. The intermediate portion 27 is placed overthe tube and may be connected to particularly the proximal portion 26with the proximal end 28. It may be sufficient if the intermediateportion 27 is attached to the proximal portion 26 by friction fit but asecure and fluid tight attachment may be preferred.

During operation of the blood pump, the attachment member 30, which maybe made of a felt material or the like, is fixed to the heart H, e.g.sutured, and the distal portion 25 extends into the heart H (FIG. 5a ).When the blood pump is to be removed, the tube including the proximalportion 26 and the distal portion 25 is pulled out of the heart H asshown in FIG. 5b . Since the disc 30 is securely fixed to the heart Hand the proximal end 28 of the intermediate portion 27 is attached tothe proximal portion 26, the intermediate portion 27 will unfold orstretch as shown in FIG. 5b . It will be appreciated that any fixationbetween the intermediate portion 27 and the proximal portion 26 would beappropriate that allows for this action, e.g. permanent fixation orsufficiently strong friction fit. It may be possible that the proximalend 28 of the intermediate portion 27 slides along the proximal portion26.

In order to prevent the tube from being pulled out of the heartaccidentally, security filaments 31 are provided that attach to the tubeand the attachment member 30 as shown in FIG. 5a . They are cut orotherwise separated in order to be able to retract the tube as shown inFIG. 5b . The part of the security filaments 31 that remains inside thepatient's body is kept as short as possible. More than one, such as two,three, four, five or six security filament 31 may be provided.

As in the previous embodiments, the intermediate portion 27 is twistedto provisionally close it (FIG. 5c ) to stop the blood flow through theflow cannula 24. This is done by twisting the proximal portion 26, whichrequires sufficient fixation of the intermediate portion 27 on theproximal portion 26. The intermediate portion 27 is then clamped by clip13 (FIG. 5d ). Finally, the intermediate portion 27 is cut, such thatthe entire tube including the distal portion 25 and the proximal portion26 along with the cut part of the intermediate portion 27 are removedfrom the patient. Only the attachment member 30 with a distal part ofthe intermediate portion 27 remains inside the patient attached to theheart H to close the opening in the heart H. Since only a small part ofthe flow cannula 24 remains inside the patient, irritations of thesurrounding tissue and the risk of inflammations can be reduced.

As shown in FIGS. 6 and 7 the attachment member 30 may be designed inaccordance with different embodiments. Preferably, the attachment memberis made of or comprises a material that allows suturing the attachmentmember to the patient's heart. A suitable material may be a felt or thelike. The attachment member 30 may be a disc, sheet or the like as shownin FIG. 6 and may assume any appropriate shape, such as rounded,circular, rectangular, polygonal or the like. For instance, a surgeonmay adapt the size and shape by cutting the edges of the attachmentmember 30.

In another embodiment as shown in FIG. 7, the attachment member 30 maycomprise a plurality of, such as three, four, five or six, sections 32separated by respective gaps 33. The sections 32 extend radially fromthe intermediate portion 27. Referring again to FIGS. 5c to 5e and toFIGS. 8a and 8b , providing sections 32 instead of a continuous disc orsheet has the advantage that during twisting of the intermediate portion27, the sections 32 get closer to each other and thereby twist andnarrow the punch hole in the heart tissue as indicated by arrows in FIG.8b , which reduces the wound size.

1. A flow cannula for a blood pump for supporting a patient's heart, theflow cannula comprising: a distal end of the flow cannula; a proximalend of the flow cannula opposite the distal end of the flow cannulaalong a longitudinal axis of the flow cannula, the distal end of theflow cannula configured to be connected to the patient's heart or ablood vessel in order to establish a fluid communication between theblood pump and the patient's heart and blood vessel, respectively; adistal portion of the flow cannula including the distal end of the flowcannula; a proximal portion of the flow cannula including the proximalend of the flow cannula; and an intermediate portion attached to atleast one of the distal portion of the flow cannula and the proximalportion of the flow cannula, wherein the intermediate portion allowstwisting thereof with a lower force than at least one of the distalportion of the flow cannula and the proximal portion of the flowcannula; wherein the intermediate portion is configured to be fullyoccluded by twisting thereof; and wherein at least a portion of theintermediate portion, alone or in combination with the distal portion ofthe flow cannula, is configured to be permanently attached to thepatient's heart or a blood vessel.
 2. The flow cannula of claim 1,wherein the intermediate portion has a distal end and a proximal end,the distal end of the intermediate portion being attached to the distalportion of the flow cannula and the proximal end of the intermediateportion being attached to the proximal portion of the flow cannula. 3.The flow cannula of claim 1, wherein the intermediate portion isattached to at least one of the distal portion of the flow cannula andthe proximal portion of the flow cannula in a fluid tight manner inorder to conduct a blood flow between the distal portion of the flowcannula and the proximal portion of the flow cannula.
 4. The flowcannula of claim 1, wherein the intermediate portion is attached to thedistal portion of the flow cannula and the proximal portion of the flowcannula such that the intermediate portion at least partially overlapsat least one of the distal portion of the flow cannula and proximalportion of the flow cannula.
 5. The flow cannula of claim 1, wherein thedistal portion of the flow cannula and the proximal portion of the flowcannula are releasably connected to each other.
 6. The flow cannula ofclaim 5, wherein the intermediate portion is axially gathered when thedistal portion of the flow cannula and the proximal portion of the flowcannula are connected to each other.
 7. The flow cannula of claim 1,wherein the intermediate portion comprises an attachment member at adistal end of the intermediate portion, the attachment member configuredto be attached to the patient's heart, wherein a proximal end of theintermediate portion is attached to the proximal portion of the flowcannula.
 8. The flow cannula of claim 1, wherein the intermediateportion is attached to the distal portion of the flow cannula and theproximal portion of the flow cannula such that the distal portion of theflow cannula and the proximal portion of the flow cannula are axiallyspaced from each other and the intermediate portion is disposed betweenthe distal portion of the flow cannula and the proximal portion of theflow cannula.
 9. The flow cannula of claim 1, wherein the intermediateportion is a flexible tubular member.
 10. The flow cannula of claim 1,wherein the intermediate portion is stretchable in a direction of thelongitudinal axis of the flow cannula.
 11. The flow cannula of claim 1,wherein the intermediate portion has a wall thickness of about 5 μm toabout 1,000 μm.
 12. The flow cannula of claim 1, wherein theintermediate portion comprises a tubular polymer film configured toinduce tissue ingrowth into the tubular polymer film.
 13. A blood pumpfor supporting a patient's heart, the blood pump comprising: a pumpcasing including at least a first inlet and a first outlet; an impellerdisposed in the pump casing, the impeller configured to draw blood intothe pump casing; an outflow cannula having a proximal end and a distalend, the proximal end of the outflow cannula coupled to the pump casingat the first outlet, the distal end of the outflow cannula configured tobe attached to a patient's aorta; and an inflow cannula coupled to thepump casing at the first inlet, the inflow cannula comprising: a distalend of the inflow cannula; a proximal end of the inflow cannula oppositethe distal end of the inflow cannula along a longitudinal axis of theinflow cannula, the distal end of the inflow cannula configured to beconnected to the patient's heart or a blood vessel in order to establisha fluid communication between the blood pump and the patient's heart andblood vessel, respectively; a distal portion of the inflow cannulaincluding the distal end of the inflow cannula; a proximal portion ofthe inflow cannula including the proximal end of the inflow cannula; andan intermediate portion attached to at least one of the distal portionof the inflow cannula and the proximal portion of the inflow cannula,wherein the intermediate portion allows twisting thereof with a lowerforce than at least one of the distal portion of the inflow cannula andthe proximal portion of the inflow cannula; wherein the intermediateportion is configured to be fully occluded by twisting thereof; andwherein at least a portion of the intermediate portion, alone or incombination with the distal portion of the inflow cannula, is configuredto be permanently attached to the patient's heart or a blood vessel. 14.The blood pump of claim 13, wherein the blood pump is sized andconfigured to be placed in the patient's thoracic cavity.
 15. A system,comprising: a flow cannula comprising: a distal end of the flow cannula;a proximal end of the flow cannula opposite the distal end of the flowcannula along a longitudinal axis of the flow cannula, the distal end ofthe flow cannula configured to be connected to the patient's heart or ablood vessel in order to establish a fluid communication between theblood pump and the patient's heart and blood vessel, respectively; adistal portion of the flow cannula including the distal end of the flowcannula; a proximal portion of the flow cannula including the proximalend of the flow cannula; and an intermediate portion attached to atleast one of the distal portion of the flow cannula and the proximalportion of the flow cannula, wherein the intermediate portion allowstwisting thereof with a lower force than at least one of the distalportion of the flow cannula and the proximal portion of the flowcannula; wherein the intermediate portion is configured to be fullyoccluded by twisting thereof; and wherein at least a portion of theintermediate portion, alone or in combination with the distal portion ofthe flow cannula, is configured to be permanently attached to thepatient's heart or a blood vessel; and at least one clip sized andconfigured to be placed around the intermediate portion of the flowcannula in order to fully occlude the flow cannula.
 16. A method forremoving a blood pump from a patient, wherein the blood pump is in fluidcommunication with the patient's heart or a blood vessel via a flowcannula, the flow cannula comprising a distal end and a proximal endopposite the distal end along a longitudinal axis of the flow cannula,the distal end of the flow cannula connected to the patient's heart inorder to establish the fluid communication between the blood pump andthe patient's heart, the flow cannula comprising a distal portionincluding the distal end and a proximal portion including the proximalend, the flow cannula further comprising an intermediate portionattached to at least one of the distal portion and the proximal portion,the method comprising: twisting the intermediate portion such that theintermediate portion is fully occluded to stop a blood flow through theflow cannula.
 17. The method of claim 16, further comprising: attachinga clip around the twisted intermediate portion to definitely occlude theflow cannula.
 18. The method of claim 16, further comprising: removingthe proximal portion of the flow cannula by separating the intermediateportion at a location proximal with respect to the clip, wherein atleast a portion of the intermediate portion, alone or in combinationwith the distal portion, remains permanently attached to the patient'sheart.
 19. The method of claim 16, further comprising before twistingthe intermediate portion: separating the proximal portion and distalportion; and axially moving the proximal portion and distal portionapart from each other.
 20. The method of claim 16, further comprisingbefore twisting the intermediate portion: unfolding or stretching theintermediate portion.
 21. (canceled)
 22. The flow cannula of claim 4,wherein the intermediate portion at least partially overlaps each of thedistal portion of the flow cannula and the proximal portion of the flowcannula.
 23. The flow cannula of claim 7, wherein the distal portion ofthe flow cannula and the proximal portion of the flow cannula areintegrally formed.
 24. The flow cannula of claim 11, wherein theintermediate portion has a wall thickness of less than about 150 μm. 25.The flow cannula of claim 11, wherein the intermediate portion has awall thickness of less than about 50 μm.
 26. The flow cannula of claim11, wherein the intermediate portion has a wall thickness of about 30μm.
 27. The flow cannula of claim 12, wherein the tubular polymer filmcomprises polyethylene terephthalate.
 28. The flow cannula of claim 1,wherein the intermediate portion comprises a polymer tube configured toinduce tissue ingrowth into the polymer tube.
 29. The flow cannula ofclaim 28, the polymer tube comprising one of silicone or polyurethane.30. The system of claim 25, further comprising a blood pump, the bloodpump comprising: a pump casing including at least a first inlet and afirst outlet; an impeller disposed in the pump casing, the impellerconfigured to draw blood into the pump casing; and an outflow cannulahaving a proximal end and a distal end, the proximal end of the outflowcannula coupled to the pump casing at the first outlet, the distal endof the outflow cannula configured to be attached to a patient's aorta;wherein the pump casing is coupled to the flow cannula at the firstinlet.